(1) Field of the Invention
This invention relates to a highly weather-resistant electrodeposition coating composition, and more particularly to a highly weather-resistant electrodeposition coating composition which is capable of imparting an excellent weather resistance to an anodized aluminium or aluminium alloy material (hereinafter simply referred to as an aluminium material) by one electrodeposition coating alone.
(2) Description of the Prior Art
As an example of the electrodeposition coating compositions used for coating the aluminium material, there has been known an acrylic-melamine based water-soluble or water-dispersible coating composition, for example, there is used a water-soluble or water-dispersible coating composition which is obtained by mixing melamine resin as a crosslinking agent with a water-soluble or water-dispersible resin formed by neutralizing a polycarboxylic resin obtained by copolymerization of acrylic acid or methacrylic acid with other acrylic unsaturated monomer and/or ethylenically unsaturated monomer with ammonia or organic amine. The acrylic-melamine based electrodeposition coating composition has widely been used in coating building materials such as an aluminium sash used in the general houses and high buildings due to its good corrosion resistance and weather resistance.
However, although the acrylic-melamine based electrodeposition coating composition exhibits a satisfactory weather resistance when used in the general houses, the electrodeposition coating composition is quite incapable of satisfying recent requirements for durability over a long period of time of several decades when applied to building materials for use in buildings. Accordingly, development of an improved coating composition over the conventional electrodeposition coating composition is highly demanded.
There has heretofore been known a fluorocarbon polymers based coating composition which is capable of forming a film guaranteed for 20 to 30 years as a coating composition to form a highly durable film. The fluorocarbon polymers based coating composition is to be usually coated by coating means such as air spray coating, electrostatic spray coating and roll coating, and is impossible to be uniformly coated on a substrate having complicated shapes such as the aluminium sash, resulting in that a required film thickness is not obtained uniformly, for instance, when applied to an inner portion of a concave surface and in that problems are produced in quality assurance.